Contact

Porträt Prof. Dr. Kvashnina, Kristina; FWOS

Prof. Dr. Kristina Kvashnina

Head of the Synchrotron Science Department
Responsible for the BM20 (ROBL) beamline at ESRF

Phone: +33 476 88 2367

Department of Molecular Structures

Molecular Structures

Research

The Department of Molecular Structures conducts synchrotron-based research, offering a robust toolkit for scientists investigating materials containing actinides and lanthanides.

Experiments take place at the Rossendorf Beamline of The European Synchrotron (ESRF), in Grenoble (France) which is specifically dedicated to the actinide science and research on radioactive waste disposal. The beamline consists of four experimental stations -XAFS, XES, XRD-1, XRD-2:

  • XAFS station with fluorescence and transmission detection for X-ray Absorption Fine-Structure (XAFS) spectroscopy, including (conventional) X-ray Absorption Near-Edge Structure (XANES) and Extended X-ray absorption fine-structure (EXAFS) spectroscopies
  • XES with a 5-crystal Johann-type spectrometer for high-energy-resolution fluorescence-detection X-ray absorption near-edge spectroscopy (HERFD-XANES), X-ray emission spectroscopy (XES) and resonant inelastic X-ray scattering (RIXS) measurements.
  • XRD-1 station with a heavy-duty, Eulerian cradle, 6-circle goniometer for (high-resolution) powder X-ray diffraction (PXRD), surface-sensitive crystal truncation rod (CTR) and resonant anomalous X-ray reflectivity (RAXR) measurements
  • XRD-2 station with a Pilatus3 x2M detector stage for single crystal X-ray diffraction (SCXRD) and in situ/in-operando PXRD measurements.

Our research provides detailed insights into the structural and electronic properties of actinide and lanthanide-containing materials across various scientific disciplines, including physics, chemistry, environmental science, and geoscience. We study fundamental electron interactions, bonding properties, probing the local structures and oxidation states of complex systems. Data analysis is performed with the help of electronic structure calculations. 

EXAFS, HERFD-XANES, XES and RIXS is not restricted to crystalline solids, but can be applied to a wide range of samples, to derive information on e.g. aqueous speciation, complexation with dissolved inorganic ligands like chloride, sulfate or nitrate, complexation with organic ligands like acetate or humic acid, interaction with bacteria and plants, sorption to mineral and rock surfaces for actinides an other metals and metalloids. Due to the high penetration depth of the employed hard X-rays, the methods are suited to study chemical reactions in-situ/in-operando, for instance at very low or high temperatures, under special atmospheres, or under electrochemical potentials.

More about Rossendorf Beamline

Latest publication

Exploring metastable phases in cerium-doped zirconia: Insights from X-ray diffraction, Raman and Luminescence spectroscopy

Braga Ferreira dos Santos, L.; Svitlyk, V.; Richter, S.; Hennig, C.; Müller, K.; Bazarkina, E.; Kvashnina, K.; Stumpf, T.; Huittinen, N. M.

Abstract

The ZrO2-CeO2 system is crucial for various applications, but discrepancies persist regarding the miscibility of the cations and the occurrence of metastable phases in the Zr1-xCexO2 phase diagram. This work aimed to close these knowledge gaps by conducting detailed investigations of Zr1-xCexO2 compositions with varying cerium concentrations and incorporating Eu3+ as a luminescent probe. Synchrotron powder X-ray diffraction analysis revealed a miscibility gap between 20 and 50 mol% cerium, where two stoichiometric Zro.80Ce0.20O2 and Zro.50Ceo.50O2 phases coexist. Outside of this miscibility gap, solid solutions were found and various crystalline phases were identified, including monoclinic (m), tetragonal (t), tetragonal prime (t’), tetragonal double prime (t’’), and cubic (c), depending on the cerium concentration. The existence of the t’ and t’’ phases was confirmed through normalized lattice parameter an, and z(O) coordinates. Raman investigations revealed a distinct distortion band in all compositions containing the t’ phase. Contrary to existing literature, the HERFD-XANES demonstrated that the presence of the feature associated with distortion in Raman spectroscopy is not related to Ce3+, but is likely a result of the oxygen displacement in the t’ structure. Finally, luminescence spectroscopy of the europium environment in the samples revealed distinct excitation and emission spectra across the various crystal phases, enabling the unambiguous distinction of the metastable phases for the first time. This study reveals the complex binary ZrO2-CeO2 system, with several structural polymorphs. The ability to precisely control the phase composition offers immense potential for tuning the properties for different applications, such as in the SOFCs fields.

Keywords: ZrO2-CeO2 solid solutions; miscibility gap; D-band; tetragonal metastable phase; relative symmetry

Involved research facilities

Related publications

Permalink: https://www.hzdr.de/publications/Publ-40057

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Team

Head

NameBld./Office+49 351 260Email
Prof. Dr. Kristina KvashninaROBL/21.6.04+33 476 88 2367

Employees

NameBld./Office+49 351 260Email
Dr. Lucia AmidaniROBL/14.1.04+33 476 88 1982
Dr. Nils BaumannROBL/21.6.03+33 476 88 2849
Clara Lisa E SilvaROBL/14.1.04+33 476 88 2044
Jörg ExnerROBL/BM20+33 476 88 2372
Dr. Christoph HennigROBL/21.6.02a+33 476 88 2005
Dr. Eleanor Sophia Lawrence Bright+33 476 88 2462
Dr. Damien PrieurROBL/21.6.03+33 476 88 2463
Dr. André Roßberg801/P3162758
Anne Thielena.thielenAthzdr.de
Dr. Sami Juhani Vasalas.vasalaAthzdr.de